Abstract
Stilbene synthase is a key enzyme for the production of the phytoalexin resveratrol. Some clones of Vitis sylvestris, a wild European grapevine species which is almost extinct, have been shown to accumulate more resveratrol in response to different forms of stress. In the current study, we asked whether the induction of stilbene synthase transcripts in Hoe29, one of the V. sylvestris clones with elevated stilbene inducibility, might result from the elevated induction of the transcription factor MYB14. The MYB14 promoter of Hoe29 and of Ke83 (a second stilbene-inducible genotype) harboured distinct regions and were applied to a promoter-reporter system. We show that stilbene synthase inducibility correlates with differences in the induction of MYB14 transcripts for these two genotypes. Both alleles were induced by UV in a promoter-reporter assay, but only the MYB14 promoter from Hoe29 was induced by flg22, consistent with the stilbene synthase expression of the donor genotypes, where both respond to UV but only Hoe29 is responsive to Plasmopara viticola during defence. We mapped upstream signals and found that a RboH-dependent oxidative burst, calcium influx, a MAPK cascade, and jasmonate activated the MYB14 promoter, whereas salicylic acid was ineffective. Our data suggest that the Hoe29 allele of the MYB14 promoter has potential as a candidate target for resistance breeding.
Highlights
Grapevine is an economically important crop, which is highly susceptible to various biotic diseases, and, requiring extensive plant protection measures
Both alleles were induced by UV in a promoter–reporter assay, but only the MYB14 promoter from Hoe29 was induced by flg22, consistent with the stilbene synthase expression of the donor genotypes, where both respond to UV but only Hoe29 is responsive to Plasmopara viticola during defence
Using a promoter–reporter assay in grapevine suspension cells (Höll et al, 2013), we show that differences in the inducibility of the MYB14 promoter can account for the stress-specific differences in the expression of stilbene synthase observed between the three genotypes (Hoe29, Ke83, and Augster Weiss)
Summary
Grapevine is an economically important crop, which is highly susceptible to various biotic diseases, and, requiring extensive plant protection measures. An important element for sustainable viticulture is resistance breeding using resistance factors originating from North American grapes (Gessler et al, 2011) These resistance factors have to be understood in context with the complex evolution of plant immunity: The plant. The first layer exploits ubiquitous molecules in pathogenic microorganisms, termed pathogenassociated molecular patterns (PAMPs), to recognize pathogen attack by receptors at the plasma membrane and to activate a basal, so-called PAMP triggered immunity, PTI (Jones and Dangl, 2006; Boller and He, 2009). Most of these PAMPs are essential for the life cycle of the invader, such that the PAMPs are preserved. The molecular mechanisms underlying these two layers of plant immunity differ, but can overlap (Thomma et al, 2011), which contributes to the complexity of the plant–pathogen interaction
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